JP2017168488A - Manufacturing method of multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the thickness of an external electrode, in a manufacturing method of multilayer ceramic capacitor, where an unbaked component body and a conductive paste film, formed on the surface thereof and becoming an external electrode, are fired at the same time.SOLUTION: Prior to a process for forming a conductive paste film becoming external electrodes 12 and 13, a process for heat-treating an unbaked component body 2 in the unfired stage of the component body 2, and removing an organic material exposed to the surface of the unbaked component body 2 is carried out. As a result, fine irregularities and holes are generated on the surface of the unbaked component body 2, and the surface of the component body 2 can be made porous. Consequently, conductive paste becomes hard to flow, and the conductive paste film is less likely to become thin locally at specific parts, e.g., the edge line and corner of the component body 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a multilayer ceramic capacitor, and in particular, in manufacturing a multilayer ceramic capacitor, an external electrode formed using a conductive paste is fired simultaneously with a component body. It is about.

  A typical multilayer ceramic capacitor includes a plurality of laminated dielectric ceramic layers and an inner electrode formed along a specific interface between the dielectric ceramic layers, at the edge of a component body and a specific one of the internal electrodes. And an external electrode formed on the end of the component main body so as to be electrically connected.

  As an example of a method for manufacturing such a multilayer ceramic capacitor, Japanese Patent Application Laid-Open No. 2001-15376 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2006-86400 (Patent Document 2) include an unfired stage of a component body. There is a method in which a conductive paste film to be an external electrode is formed on the surface of a component main body, and then an unfired component main body and the conductive paste film are simultaneously fired.

JP 2001-15376 A JP 2006-86400 A

  When attempting to reduce the thickness or thickness of a multilayer ceramic capacitor, it is effective to reduce the thickness of the external electrodes. However, if the conductive paste film to be the external electrode is thinly formed in order to make the external electrode thin, the external electrode becomes thin particularly on the ridge line or corner of the component body as a result of simultaneous firing with the unfired component body. It is easy to become, and in extreme cases, it may be interrupted. This leads to a decrease in the reliability of the multilayer ceramic capacitor.

  Accordingly, an object of the present invention is to provide a method for manufacturing a multilayer ceramic capacitor capable of stably maintaining the thickness of an external electrode.

  The present invention includes a step of producing an unfired component body containing a ceramic raw material and an organic material, a step of forming a conductive paste film to be an external electrode on the surface of the unfired component body, and an unfired component body And a step of simultaneously firing the conductive paste film, the method is directed to a method for manufacturing a multilayer ceramic capacitor, and in order to solve the above technical problem, before the step of forming the conductive paste film The method further comprises the step of removing organic substances exposed on the surface of the unfired component body.

  The organic matter described above is mainly a binder, but as a result of removing the organic matter exposed on the surface of the unfired component body, fine irregularities and pits are generated on the surface of the component body, making the surface of the component body porous. can do.

  In the step of removing the organic matter, it is sufficient that at least a part of the organic matter is removed, and it is not necessary to remove all the organic matter.

  In the step of forming the conductive paste film to be the external electrode described above, particularly when the conductive paste film is formed in a state of straddling the ridgeline where at least two surfaces of the component body intersect, the present invention Applied advantageously. This is because the external electrode tends to be thin or broken on the ridgeline or corner of the component body.

  In the present invention, preferably, the unfired component body includes a step of producing a laminate block in which an unfired ceramic layer containing a ceramic raw material and an organic material is laminated, and a laminate block for obtaining a plurality of unfired component bodies. And the step of cutting. In this case, before the step of cutting the laminated block, a step of removing organic substances exposed on the surface of the unfired component main body may be performed in the state of the laminated block. According to this structure, the process of removing organic substance can be advanced efficiently.

  For example, heating is applied to remove organic matter. In this case, it is preferable to heat the green part body at a temperature lower than the maximum temperature applied in the firing step. When heating is applied to remove organic matter, removal of organic matter can be performed at once for a large number of component bodies or for a laminated block having a large area. Further, if the heating is performed at a temperature lower than the maximum temperature applied in the firing step, ceramic oversintering can be prevented.

  More preferably, the said heating is implemented at the temperature of 100 degreeC or more and 900 degrees C or less. Here, the lower limit of 100 ° C. is a temperature at which the organic substance starts to burn out, and the upper limit of 900 ° C. is a temperature at which the ceramic does not sinter excessively.

  In order to remove the organic matter, the unfired component body may be subjected to chemical etching or physical etching instead of the heating described above. Such chemical etching or physical etching is advantageously applied particularly to the above-described laminated block from which a plurality of green part bodies can be taken out. This is because when the heating step is performed on the laminated block, the laminated block may be undesirably warped.

  The conductive paste film to be the external electrode preferably contains Ni powder and ceramic powder in order to allow simultaneous firing with the unfired component body.

  The method for manufacturing a multilayer ceramic capacitor according to the present invention is a modification in which a silicon compound or a fluorine compound is adsorbed on the surface of an unfired component body after a step of removing organic substances and before a step of forming a conductive paste film. It is preferable to further comprise a processing step. By this modification treatment, the shape of the conductive paste film can be further stabilized in the next step of forming the conductive paste film.

  According to the present invention, the organic matter exposed on the surface of the unfired component body is removed. As a result, fine irregularities and pits are generated on the surface of the component body, and the surface of the component body is made porous. Thus, a conductive paste film to be an external electrode is formed. Therefore, the following effects are exhibited.

  Due to the anchor effect on the surface of the porous component main body, the conductive paste tends to adhere to the ridgeline and corner portions of the component main body, and after adhering, the conductive paste is less likely to flow and is easily held in place. Also, due to the capillary action on the surface of the porous component body, the solvent in the conductive paste is absorbed by the component body side, and accordingly, the viscosity of the conductive paste increases, and this also causes the conductive paste to flow. It becomes difficult to hold, and it becomes easy to be held on the spot.

  As a result, the conductive paste film is unlikely to become thin locally, and for example, the thickness of the conductive paste film can be maintained in the same manner as on other parts even on the ridge lines and corners of the component body. .

1 is a perspective view showing an appearance of a multilayer ceramic capacitor 1 as a first example obtained by the manufacturing method according to the present invention. It is sectional drawing which follows the line AA of FIG. It is the drawing substitute photograph which image | photographed the surface of the unbaked component main body with the field emission type scanning electron microscope, (A) shows the state before removing organic substance, (B) is the state after removing organic substance Indicates. It is a perspective view which shows the external appearance of the multilayer ceramic capacitor 21 as a 2nd example obtained by the manufacturing method which concerns on this invention. It is a top view which shows the external appearance of the multilayer ceramic capacitor 31 as a 3rd example obtained by the manufacturing method which concerns on this invention.

  A multilayer ceramic capacitor 1 obtained by the manufacturing method according to the present invention will be described with reference to FIGS.

  The multilayer ceramic capacitor 1 includes a component body 2. The component main body 2 has a substantially rectangular parallelepiped shape having six surfaces, and first and second main surfaces 3 and 4 opposed to the height direction H, and first and second side surfaces 5 and 6 opposed to the width direction W. , And first and second end faces 7 and 8 facing in the length direction L. Here, the height direction H, the width direction W, and the length direction L are orthogonal to each other. The substantially rectangular parallelepiped shape of the component body 2 includes a shape in which corners and ridge lines of the rectangular parallelepiped are rounded, and also includes a shape in which slight irregularities are formed on the surface.

  The component body 2 includes a plurality of laminated ceramic layers 9 and a plurality of internal electrodes 10 and 11 formed along a specific interface between the plurality of ceramic layers 9.

Each ceramic layer 9 has an average thickness of 0.5 μm to 4 μm, for example. The ceramic layer 9 is made of, for example, a dielectric ceramic mainly composed of barium titanate (BaTiO ₃ ), calcium titanate (CaTiO ₃ ), strontium titanate (SrTiO ₃ ), or calcium zirconate (CaZrO ₃ ). . The ceramic layer 9 may also contain Mn, Mg, Si, Co, Ni, a rare earth element, or the like as an auxiliary component having a smaller content than the main component.

  The internal electrodes 10 and 11 are formed so that the edge of the internal electrodes 10 and 11 is exposed to one of the end surfaces 7 and 8 of the component body 2, but the first internal electrode 10 exposed to the first end surface 7 of the component body 2. And the second internal electrodes 11 exposed on the second end face 8 are alternately arranged in the height direction H so that the electrostatic capacity can be obtained through the ceramic layer 3 inside the component body 2. .

  The internal electrodes 10 and 11 have a substantially rectangular shape in plan view in the height direction H. Each of internal electrodes 10 and 11 has an average thickness of 0.2 μm to 2 μm, for example. The internal electrodes 10 and 11 include, for example, a metal material such as Ni, Cu, Ag, Pd, an Ag—Pd alloy, or Au.

  In order to take out the capacitance described above, first external electrodes electrically connected to the first internal electrode 10 are respectively provided on the first and second end faces 7 and 8 facing each other of the component body 2. 12 and a second external electrode 13 electrically connected to the second internal electrode 11 are formed. The external electrodes 12 and 13 are formed, for example, by baking a conductive paste containing Ni powder and ceramic powder, and are formed by simultaneous firing with the component body 2 as described later.

  The first and second external electrodes 12 and 13 are not only on the first and second end surfaces 7 and 8 of the component main body 2 but also the main surfaces 3 and 4 and side surfaces adjacent to the end surfaces 7 and 8, respectively. 5 and 6 are formed so as to extend to each part. In other words, the external electrodes 12 and 13 are formed so as to straddle the ridge line of the component body 2. Further, the external electrodes 12 and 13 formed in a state straddling the ridge line of the component main body 2 naturally cover the corners of the component main body 2.

  A plating film is formed on the external electrodes 12 and 13 as necessary. The plating film is composed of, for example, a Cu plating film, or a Cu plating layer, a Ni plating layer thereon, and a Sn plating layer thereon. When this multilayer ceramic capacitor 1 is embedded in, for example, a multilayer substrate, only the Cu plating film is used as the plating film, and when it is used as a surface mount component, the Cu plating layer, the Ni plating layer, and the Sn plating layer are used. A plating film is applied.

  Note that the above-described Cu plating film or Cu plating layer may have a two-layer structure. In this case, the average particle diameter of the Cu particles of the second Cu plating layer directly covering the first Cu plating layer is larger than the average particle diameter of the Cu particles of the first Cu plating layer directly covering the external electrodes 12 and 13. Is reduced. The average thickness of each of the first and second Cu plating layers is, for example, about 1 μm to 15 μm.

  When the multilayer ceramic capacitor 1 is reduced in size or thickness, it is preferable that the following dimensional relationship is satisfied. That is, when the dimension in the height direction H of the component body 2 is DH and the dimension in the width direction W is DW, (1/5) DW ≦ DH ≦ (1/2) DW or DH <0.3 mm. Preferably it is satisfied.

  In addition, it is preferable that the length of each of the external electrodes 12 and 13 in the length direction L is as long as possible. As a result, even if the surface-mounted multilayer ceramic capacitor 1 is thin, the adhesion force to the mounting substrate can be increased, or via connection of the multilayer ceramic capacitor 1 embedded in the multilayer substrate is facilitated.

  In order to manufacture such a multilayer ceramic capacitor 1, the following steps are performed.

  A ceramic slurry in which a ceramic raw material powder, an organic material, a solvent, and the like are mixed is formed on a carrier film by printing, spray coating, die coating, or the like to obtain a ceramic green sheet to be the ceramic layer 9. The obtained ceramic green sheet contains ceramic raw material powder, organic matter, and residual solvent. The organic substance functions as a binder such as a polyvinyl butyral resin or a phthalate resin.

  Next, a conductive film to be the internal electrodes 10 and 11 is formed on the ceramic green sheet by screen printing or gravure printing.

  Next, the required number of ceramic green sheets with conductive films are stacked, and an appropriate number of ceramic green sheets without conductive films are stacked on the top and bottom, and these are stacked in a stacking direction by rigid press or isostatic pressing. To obtain a laminated block.

  Next, the laminated block is cut by pressing, dicing, or the like, thereby obtaining a plurality of chip-shaped unfired component bodies 2.

  Next, a step of removing organic substances, which is a characteristic configuration of the present invention, is performed. Specifically, the unfired component main body 2 is heated to burn off organic substances exposed on the surface of the component main body 2. The heating temperature is set to a temperature lower than the maximum temperature applied in the baking step to be performed later. Preferably, the heating temperature is a temperature at which the organic substance starts to be burned out, which is a temperature sufficient to remove the organic substance, which is 100 ° C. or higher, and a temperature at which the ceramic does not sinter too much, or 900 ° C. or lower. preferable.

  FIG. 3 is a drawing-substituting photograph in which the surface of an unfired component main body is photographed with a field emission scanning electron microscope (FE-SEM), and (A) shows a state before organic substances are removed. ) Shows the state after removing organic matter. When (A) and (B) are compared, in (B) after removing the organic matter, the surface organic matter (resin) flies, the ceramic particles appear more clearly, and the surface becomes rough. I understand that.

  Next, it is preferable to carry out a modification treatment step in which a silicon compound or a fluorine compound is physically adsorbed or chemically adsorbed on the surface of the unfired component body 2 by using a method such as immersion in a solution or plasma treatment, for example. . By this modification treatment, the shape of the conductive paste film can be further stabilized in the step of forming the conductive paste film to be the next external electrodes 12 and 13.

  Next, a conductive paste film to be the external electrodes 12 and 13 is formed on the surface of the unfired component body 2 by, for example, a dipping method. As the conductive paste used here, a conductive paste in which Ni powder and ceramic powder are added to an organic solvent is used.

  Next, the unfired component body 2 on which the conductive paste film is formed is fired. That is, the unfired component body 2 and the conductive paste film are fired simultaneously. Thereby, the component main body 2 in which the external electrodes 12 and 13 are formed is obtained. The firing temperature is preferably 1000 ° C. or higher and 1500 ° C. or lower, which is a temperature sufficient for sintering the ceramic.

  Thereafter, as described above, a Cu plating film or a plating film made of a Cu plating layer, a Ni plating layer, and a Sn plating layer is formed on the external electrodes 12 and 13 as necessary.

  The multilayer ceramic capacitor 1 is completed as described above.

  In order to confirm the effect of the above-described organic substance removing step, the following experiment was performed.

  As a sample, a multilayer ceramic capacitor having a length direction dimension × width direction dimension × height direction dimension after firing of 1.0 mm × 0.6 mm × 0.25 mm was selected.

  A laminate obtained by performing a heat treatment at 150 ° C. for 120 minutes at the stage of an unfired component body, then forming a conductive paste film to be an external electrode, and simultaneously firing the conductive paste film and the component body A ceramic capacitor was taken as an example. On the other hand, a comparative example of a multilayer ceramic capacitor obtained by forming a conductive paste film to be an external electrode without performing heat treatment at the stage of an unfired component body and firing the conductive paste film and the component body simultaneously It was.

  When 20 multilayer ceramic capacitors according to the obtained example and 20 multilayer ceramic capacitors according to the comparative example were checked for discontinuity of the external electrode at the ridge line portion of the component body, 20 samples were obtained in the example. In all of the samples, no disconnection of the external electrode was observed, whereas in the comparative example, the disconnection of the external electrode was observed in all 20 samples.

  Hereinafter, other embodiments will be described.

First, in order to remove organic substances, the unfired component body 2 may be subjected to chemical etching or physical etching instead of the above-described heating. Chemical etching includes a solution for dissolving organic substances and plasma cleaning using O ₂ radicals. In plasma cleaning (O ₂ radical treatment), C and O on the surface of the unfired component body 2 react to remove C. In the physical etching (plasma treatment), for example, plasma cleaning (Ar etching treatment) is performed in which Ar ions are hit against the surface of the unfired component body 2 and etched.

  In the manufacturing method described above, the step of removing the organic substances exposed on the surface of the unfired component body 2 was performed after the laminated block was cut to obtain a plurality of unfired component bodies 2. Before the step of cutting the laminated block, a step of removing organic substances exposed on the surface of the unfired component body 2 may be performed in the state of the laminated block. If this process order is followed, the process of removing an organic substance can be advanced efficiently.

  In addition, when the above-described process order is adopted, in the unfired component body 2 obtained by cutting the laminated block, the organic matter is removed from only the main surfaces 3 and 4, and the end surfaces 7 and 8 corresponding to the cut surface and For the side surfaces 5 and 6, the organic matter is not removed. From this, it should be understood that the effects of the present invention can be sufficiently expected if the organic substances are removed only on the main surfaces 3 and 4.

  The above-described chemical etching or physical etching is advantageously applied particularly to a laminated block from which a plurality of unfired component bodies 2 can be taken out. This is because when the heating step is performed on the laminated block, the laminated block may be undesirably warped.

  The multilayer ceramic capacitor to which the present invention can be applied is not limited to the one such as the multilayer ceramic capacitor 1 shown in FIGS. For example, the present invention can be applied to the multilayer ceramic capacitor 21 shown in FIG. 4 and the multilayer ceramic capacitor 31 shown in FIG. 4 and 5, elements corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The multilayer ceramic capacitor 21 shown in FIG. 4 further includes third external electrodes 22 and 23 formed at an intermediate position in the length direction L of the component body 2, and constitutes a three-terminal type capacitor. It is a feature. In manufacturing such a multilayer ceramic capacitor 21, the conductive paste film to be the external electrodes 12, 13, 22, and 23 is formed after the step of removing organic substances exposed on the surface of the unfired component body 2. The conductive paste film and the component body 2 are fired at the same time.

  Third external electrodes 22 and 23 are formed so as to extend from above first and second side surfaces 5 and 6 to a part of each of first and second main surfaces 3 and 4. That is, at the stage where the component body 2 is not fired, the conductive paste films to be the third external electrodes 22 and 23 are the first and second main surfaces and the first and second side surfaces 5 and 6, respectively. It is formed in a state straddling the ridgeline where each of 3 and 4 intersects. And by carrying out the step of removing the organic matter described above, the thickness of the conductive paste film on the ridgeline of the component body 2 can be maintained at a predetermined level or more for the third external electrodes 22 and 23 as well. Therefore, it is possible to make it difficult to generate interruptions.

  Even when the third external electrodes 22 and 23 are arranged so as to go around the side surfaces 5 and 6 and the main surfaces 3 and 4 of the component main body 2 as shown by a two-dot chain line in FIG. If a step of removing organic substances exposed on the surface of the unfired component main body is performed during the manufacturing process, the same effect can be obtained.

  The multilayer ceramic capacitor 31 shown in FIG. 5 has island-shaped first and second external electrodes 32 and 33 formed on the first main surface 3 of the component body 2. That is, here, the conductive paste film to be the external electrodes 32 and 33 is not formed so as to straddle the ridge line where the two surfaces intersect. Even in such a case, the thickness of the conductive paste film to be the first and second external electrodes 32 and 33 is uniformly maintained at a predetermined value or more by performing the above-described step of removing the organic matter. Can do. Therefore, variation in the shape of the external electrodes 32 and 33 can be reduced, and the external electrodes 32 and 33 can be formed with good reproducibility.

  The first and second external electrodes 32 and 33 described above are connected to first and second internal electrodes (not shown), for example, by via conductors.

  As described above, the present invention has been described based on the illustrated embodiments. However, each embodiment described in this specification is an exemplification, and a partial replacement or combination of configurations is possible between different embodiments. I point out that there is.

1, 21, 31 Multilayer ceramic capacitor 2 Component body 3, 4 Main surface 5, 6 Side surface 7, 8 End surface 9 Ceramic layer 12, 13, 22, 23, 32, 33 External electrode

Claims (8)

Producing an unfired component body containing ceramic raw materials and organic matter;
Forming a conductive paste film to be an external electrode on the surface of the green component body;
Simultaneously firing the unfired component body and the conductive paste film;
A method for producing a multilayer ceramic capacitor comprising:
A method for producing a multilayer ceramic capacitor, further comprising a step of removing the organic matter exposed on the surface of the unfired component body before the step of forming the conductive paste film.   The multilayer ceramic capacitor according to claim 1, wherein the step of forming the conductive paste film includes a step of forming the conductive paste film in a state of straddling a ridge line intersecting at least two surfaces of the component main body. Manufacturing method. The step of producing the unfired component main body includes:
Producing a laminated block in which an unfired ceramic layer containing a ceramic raw material and an organic material is laminated;
In order to obtain a plurality of unfired component bodies, a step of cutting the laminated block;
With
The step of removing the organic matter includes a step of removing the organic matter exposed on the surface of the unfired component main body in the state of the laminated block before the step of cutting the laminated block.
The manufacturing method of the multilayer ceramic capacitor of Claim 1 or 2.   4. The multilayer ceramic capacitor according to claim 1, wherein the step of removing the organic substance includes a step of heating the unfired component body at a temperature lower than a maximum temperature applied in the firing step. 5. Production method.   The method for manufacturing a multilayer ceramic capacitor according to claim 4, wherein the heating step includes a step of heating at a temperature of 100 ° C. or more and 900 ° C. or less.   The method for producing a multilayer ceramic capacitor according to claim 1, wherein the step of removing the organic substance includes a step of chemically etching or physically etching the unfired component body.   The method of manufacturing a multilayer ceramic capacitor according to claim 1, wherein the conductive paste film to be the external electrode includes Ni powder and ceramic powder.   The method further comprises a modification treatment step of adsorbing a silicon compound or a fluorine compound on the surface of the unfired component main body after the step of removing the organic matter and before the step of forming the conductive paste film. The manufacturing method of the multilayer ceramic capacitor in any one of thru | or 7.